Thursday, August 25, 2011

Hurricane Irene and the TD 10: August 25, Update C

Hurricane Irene:
She’s finally cleared the Bahamas after paying Grand Abaco a visit. Here’s one of those cam thingies from Rockybay on Abaco… (sent to me by Charlie in Florida). This photo was taken yesterday evening, and it looks like that they lost their internet connection early this morning. Conditions look perfect for an outdoor picnic, don’t they?

As of the last advisory she’s hanging out at around 28.3N, 77.3W, moving N at 14mph (good, she’s moving N finally!). They have kept her winds at 115mph all day, with a central pressure of 942 mb. This means she’s been a category 3 (range: 111-130mph). I still think this is an overestimate, however two aircraft found this low pressure – a NOAA plane and an Air Force plane (I completely agree with the NHC when they say that these aircraft supply very valuable data!!). Interestingly, they did not record a corresponding increase in winds, suggesting that she is not structurally as sound as she could be. The NHC say they are keeping her intensity at a cat 3 for now, but may change that if the winds do not pick up. In the IR satellite image below you can see that she’s really not symmetrical (because of wind shear and dry air), and although she has an eye, there’s not as much red and no grey meaning that cloud tops are not as high as they could be in such a storm.

Another clue that she has weakened is her upper level divergence and lower level convergence – these have both weakened since this morning as well. The other thing the satellite image shows in the large reach of this system… she’s been eating one too many donuts, hasn’t she? ;-) Her outer bands at the moment are still over the southern Bahamas to the south, and North Carolina to the north. I took a couple of photos of the outer bands over on this coast of Florida, but don’t have the time to upload them. They were obviously of award winning quality. ;-)

They have, however, downgraded her forecast intensity at landfall, with landfall as a cat 2 (range: 96-110mph) in North Carolina on Saturday.  The wind shear ahead of her will continue to increase, even though she’s over warm deep waters. It looks like at the moment she is tracking east of the forecast track actually – I hope she continues in this N and NNE (and then NE) direction tomorrow!

Tropical Depression 10:
This one now has some nice circulation in the lower half of the troposphere, but the convection isn’t quite there. Hmm… officially the NHC have this one at around 14.1N, 33.1W, moving WNW at a slightly slower 9mph. The satellite images show it at around 13.8N, 35.2W (ish – it’s night time so it’s tricky for me to see). That doesn’t match up at all. How odd. Central pressure is 1009mb, winds are 35mph (over estimate still). They have forecast this one to head NW and fizzle out in the Atlantic on Sunday at around 17N, 36W. I think it will carry on WNW for a lot longer, especially if they have it at the wrong coordinates! It is surrounded by a high pressure on all sides so I expect this to slow down a lot more, and possibly stall.

That’s it for tonight.

Blogs archived at
Twitter @JyovianStorm

DISCLAIMER: These remarks are just what I think/see regarding tropical storms - not the opinion of any organization I represent. If you are making an evacuation decision, please heed your local emergency management and the National Hurricane Center's official forecast and the National Weather Service announcements. This is not an official forecast. If I "run away, run away" (Monty Python), I'll let you know.

No comments: